Superheater tube



Dec. 30, 1930. w. B. WHITSITT ET AL 1,786,382

SUPERHEATER TUBE Filed Nov. 8,, 1926 2 Sheets-Sheet 1 w ,6 VENIOR) fi l/1% .Dec. 30, 1930. v w. B. WHITSITT ET AL SUPERHE ATER TUBE 2 Shets-Sheet 2 Filed Nov. 8, 1926 INVENT ATTORNEY.

Patented Dec. 30, 1930 WILLIAM B. WHI'l-SITT AND WALTER R.

HEDE'MAN, OF BALTIMORE, MARYLAND surnnnnernn TUBE Application filed November 8, 1926; Serial No. 147,160.

Our invention has for its object to provide a highly efiicient superheater unit for locomotive boilers'. t i

Our invention relates to that type of superheating apparatus wherein the superheater units are placed within fire fines of the boiler,

' in such manner that they are subjected to the heat fromthe productsofcombu'stion as they pass through said fiuesfi Before our invention it was the practice to use straight smooth bore superheater unitsor tubes.

p Also applications have been made with the superheater units wrapped spirally around themselves, in order to give. a whirling motion to the steam. This construction is difficult to manufacture and repair.

In superheating apparatus of this kind, it is the commonpractice to extend the super? heater units'from a saturated, or a saturated portionof a steam header, into andthen out of'the units, and thence, to a superheated, or

r a superheatedportion of a steam header.

' When steam is "passed'through the superheater units of the type known prior to our inventionthe steam in direct contact with the wall of the unit becomes superheated, but in practice it has been found that there is a central core of steam which becomes entirely surrounded by superheated steam and is insulated thereby from the applied heat and remains saturated.

By the use of our improved corrugated superheater unit, there is imparted to the saturated steam passing through it a circular motion, which results, from centrifugal force, in violently throwing the entire mass of steam against the outer wall of the corrugated superheater unit, entirely breaking up any core of saturated steam. The pitch of the helical corrugations being relatively short a very violent, revolving or whirling motion is imparted to the steam.

In the drawings: 7

Figure 1 is a detail view, partly in section, showing the general arrangements of our corrugated superheater units in a locomotive boiler.

Figure 2 is a top plan view of our superheater unit detached.

Figure 3 is a side elevation of Figure 2.

" Figures stand 5 are diagrammatic views of superheater units poses. i v ln'Figui-el of the dr for comparative purawings we have shown a general assembly view with-our improved superheater units in proper position in a locomotive structure. g i 1 Our improved superheater unit is, as shown, adapted to be placed within the firefiues 3, as is usual with structures ofthis character.

According to our invention, the superheater unit-1 consists of a seamless tube of any suitable metal into which is rolled or pressed'helical corrugations 2 having a double pitch,somewhat after the fashion of double pitch screw threads as will be clearly seen from'Figures 2 and 3. I Q By reason of the helical corrugations in the superheater unit we are enabled to use a v single instead of a double loop as has heretofore been used for superheater units, without reducing the efliciency of the unit. It follows that wears also enabled touse a tire flue of much smaller diameter than the fiues .now commonly used.

As elsewhere pointed out, it is well known that in all superheater units in use prior to .our invention therejs a core of saturated steam surrounded by superheated steam, and this core of saturated steam passes on with its jacket of superheated steam to the superheated steamheader, whereas by reasonof the fact that the pitch of the helical corrugations in our superheater unit is relatively short a very Violent motion is imparted to the saturated steam passing through the unit, imparting to the entire body of steam centrifugal force, which throws the entire mass of the steam against the outer wall of the, superheater unit, thus entirely breaking up the core of saturated steam.

In Figure '4; we have illustrated a section of a large flue A'with double loop units B of. smooth straight bore, while in Figure 5 illustrating the application of our invention, we have illustrated a. section of a flue 3 (approximately one half the diameter of flue A, Figure 4) with a single loop corrugated unit 1.

By comparison of Figures t and 5 it will be seen that the superheatingsurface may be reduced without reducing the amount of superheat imparted to the steam.

By our invention it is possible to use but twenty-one of our corrugated superheater elements or units, and get the same or better efficiency than is obtained in a boiler having twenty-eight superheater units with the smooth bore as shown in Figure 4. Obviously also our invention allows of the use of a number of units giving greatly increased gen erating capacity over that of an ordinary boiler without increasing the size of the boiler.

In other words, the advantage to be gained by the use of our helical corrugated superheater unit is a higher degree of superheat for the same number of superheater units. This more effective heating surface will allow the elimination of a certainpercentage of superheaterunits, instead of which can be applied ordinary small tubes, resulting in a greater evapo-rative heating surface. This elimination of the superheater units will result in a cheaper application and cheaper maintenance.

What we claim is:

1. In a tubular superheated steam boiler, and in combination with a smoke tube, a steam superheater tube arranged within the smoke tube and heated by the products of combustion flowing therethrough, said superheater tube having a flow-change wall surface comprising double, short-pitch, shallow helical corrugations operating to effect a whirling motion of the flowing steam in a helical path and to mix the superheated steam lying next to the tube wall withthe core of saturated steam surrounded thereby and to project the =mixed steam by centrifugal force against the wall surface to produce a rapid and substantially uniform superheating of all the steam flowing through the tube.

2. In a tubular superheated steam boiler, and in combination with a smoke tube, a U- shaped steam superheater tube arranged within the smoke tube and heated by the prodnets of combustion flowing therethrough, said tube embodying straight portions connected by a return bend for the flow of steam therein successively in opposite directions, each straight tube portion having its wall provided with a change-flow surface extending helically in the direction of steam flow therein and comprising double, short-pitch, sh allow helical corrugations operating to effect a whirling motion of the flowing steam in a helical path and to mix the superheated steam lying next to the tube Wall with the core'of saturated steam surrounded thereby and to project the mixed steam by centrifugal force against the wall surface to produce a rapid. and substantially uniform superheating of all the steam flowing through the tube.

In a t bular superh te m p en suporheater unit arranged therein and heated by the products of combustion flowing therethrough, said unit being formed of a plurality of U-shaped passes connected by U-bends for the flow of steam from one to the other and each consisting of a pair of straight tubes connected by a U-bend for the successive flow-of steam in opposite directions, each tube having its wall provided with a 'flowchange surface extending helically in the direction of steam flow therein and comprising double, shortpitch, shallow helical corrugations operating to effect a whirling motion of the flowing steam in a helical path and to mix the'superheated steam lying next to the tube wall with the core of saturated steam surrounded thereby and to project the mixed steam by centrifugal force against the wall surface to produce a rapid and substantially uniform superheating of the steam flowing through the tube.

4. In a tubular superheated steam boiler, and in combination with a smoke tube of the boiler, a superheater tube located in the smoke tube and heated by the products of combustion flowing therethrough, said superheater tube having its wall provided with a flowchange surface comprising shallow double helical corrugations of short pitch acting to impart a whirling motion to the flowing steam and to mix the outer strata of superheated steam lying next to the tube wall with the central core of saturated steam insulated by the superheated strata from said wall and to throw the mixed steam by centrifugal I force against the wall to effect a uniform superheating of all the steam,

In testimony whereof/we aifix our signatures.

WILLIAM B. WHITSITT. WALTER R. HEDEMAN.

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